This is a Shannon Award providing partial support for the research projects that fall short of the assigned institute's funding range but are in the margin of excellence. The Shannon Award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. Williams syndrome (WS) is a rare congenital neurodevelopmental disorder which is characterized at the psychological level by an unusual cognitive phenotype. Individuals with WS are typically affectionate, very interested in people, have relatively good language and face-processing skills, despite low IQ scores. This profile has led some researchers to propose that WS involves a sparing in theory of mind abilities (Karmiloff-Smith et al., in press; Tager-Flusberg et al., 1994). The proposed research program will explore theory of mind and related social- cognitive abilities in well-defined groups of WS children and adolescents. The WS subjects will be compared to two sets of mentally retarded/learning disabled (MR/LD) and normal controls: one set matched on overall mental age, the other set matched on language abilities. The main hypothesis is that the WS subjects will perform significantly better than the MR/LD subjects on tasks tapping basic theory of mind abilities, including false belief (Eexperiments 1, 2), knowledge and intention (Experiment 4), the use of mental states to explain behavior (Experiment 3), discrimination of facial expressions of affect (Experiment 6) and visual perspective-taking (Experiment 5). We also predict that they will perform significantly better than the MR/LD controls on a second-order theory of mind task (Experiment 7). In contrast, we predict that WS subjects will perform at the same level as the MR/LD controls, and significantly worse than normally developing controls on tasks tapping higher-order social-cognitive constructs that build on a basic theory of mind but which also entail additional aspects of conceptual change. This prediction will be tested in tasks tapping knowledge of lies and jokes (Experiment 8), the concepts of trait (Experiment 9) and empathy (Experiment 11), moral judgement (Experiment 10), concepts of personal and social relations (Experiment 12) and self understanding (Experiment 13). The findings from this research will have important theoretical implications for how we conceptualize the cognitive and neural mechanisms that underlie social cognition, and will advance our understanding of social development in Williams syndrome.